Metal-to-metal sealing system

ABSTRACT

A metal-to-metal sealing element for a wellhead assembly which includes at least first and second adjacent components and first and second generally annular sealing surfaces that are each formed on a corresponding one of the components. The sealing element comprises an annular base, an annular sealing lip which projects radially toward at least one of the first and second sealing surfaces and which comprises a seal retaining groove, a soft metal sealing insert which is disposed within the seal retaining groove and which in use engages the at least one sealing surface, and an annular intermediate portion which extends between the base and the sealing lip. The intermediate portion presses the sealing insert against the at least one sealing surface in an interference fit relationship.

[0001] This application is a divisional of U.S. patent application Ser.No. 09/819,121, which was filed on Mar. 27, 2001.

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to an annularmetal-to-metal sealing system for providing a fluid and pressure tightseal between two or more components of a wellhead assembly. Moreparticularly, the present invention relates to an annular sealingassembly which includes a high strength seal carrier body to which isretained an annular seal insert that is composed of a soft, corrosionresistant metal which is sufficiently deformable by seal activatingforce of the seal carrier body to conform to the surface geometry andfinish of a sealing surface and thus establish an efficient highpressure seal therewith.

[0003] Current rigid metal sealing technologies, such as Straight BoreMetal Seals (“SBMS”), Rough Casing Metal Seals (“RCMS”), FX Bonnetgaskets, and RX, BX and AX gaskets, require higher strength alloys toprovide structural integrity and sealing force. These types of seals arewidely used in gate valve bonnets, surface and subsea connectors, flowbores and generally throughout wellhead equipment. The strengthrequirements of these alloys can be up to 120,000 psi yield. These sealswork by plastically deforming a small area into a smooth opposingsurface. The seal contact area is generally small, and these seals aregenerally (with a few exceptions) not reusable. Often, due to corrosionrequirements, high strength nickel alloys are selected for these seals.These seals may be sensitive to surface finish, installation damage andgalling.

SUMMARY OF THE INVENTION

[0004] The present invention provides a high-pressure, metal-to-metalsealing system which employs a high strength metal seal body or carrierthat facilitates application of spring energy or preload force to a softmetal insert carried by the seal body to accomplish high pressuremetal-to-metal sealing even under conditions of poor surface finish orirregular sealing surface geometry. The present invention hasapplication to rigid metal-to-metal seal technology including SBMSseals, RCMS seals, FX bonnet gaskets, RX, BX and AX gaskets and others.The concept of the invention involves separating the structural element(i.e., the seal body) from the sealing element (i.e., the soft metalinsert). In such sealing systems, the soft metal insert may be installedby pressing, shrinking or other retention mechanisms on the higherstrength seal body.

[0005] The higher strength seal body elastically deforms and provides aspring energy characteristic to activate the seal, plastically deformingthe soft metal insert when installed. The high strength seal body alsoconfines and protects the soft metal insert against pressure andmechanical abuse. This type of sealing system increases the contactarea, allows lower alloy materials (such as 410 stainless steel or 8630or 4130 steel) to be used for the body, prevents galling, and alsoallows the soft metal insert to be replaced, thus enabling reuse of theseal body. The soft metal insert will also accommodate wider machiningtolerances and will seal against surfaces that have defects, such asscratches. This seal design may also be tolerant to slightly oval shapedseal bores.

[0006] The sealing concept of the present invention thus represents animprovement over metal seals that simply have a soft coating on thesurface or require the soft metal to be welded to the high strengthcomponent. Coatings have limited wear/corrosion life and cannot filllarge defects in the sealing area. In addition, welding the soft metalto the high strength component adds complexity, expense, and limitsmaterial selection and may preclude reuse of the seal.

[0007] So that the manner in which the above recited features,advantages and objects of the present invention are attained and can beunderstood in detail, a more particular description of the invention,briefly summarized above, may be had by reference to the preferredembodiment thereof which is illustrated in the appended drawings. It isto be noted however, that the appended drawings illustrate only atypical embodiment of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a fragmentary vertical section of a wellhead assemblyfor an oil or gas well, showing a number of uses of a metal-to-metalsealing system embodying the principles of the present invention;

[0009]FIG. 2 is a fragmentary section, on an enlarged scale, of ametal-to-metal sealing system according to the present inventionemployed to provide a metal-to-metal seal between a valve bonnet and avalve body, or between two line flanges or other flanged annularelements;

[0010]FIG. 3 is an enlarged fragmentary section of a metal-to-metal sealaccording to the present invention between two pipes interconnected byan external pipe coupling;

[0011]FIG. 4 is a sectional view of an annular seal body embodying theprinciples of the present invention;

[0012]FIG. 5 is a fragmentary sectional view of an end portion of theannular seal body of FIG. 4 showing an annular seal groove formed in anannular sealing projection or lip thereof and further showing a softmetal sealing element located within the annular seal groove;

[0013]FIG. 6 is a partial sectional view of an annular seal body havinga soft metal sealing insert located in annular end grooves thereof andrepresenting an alternative embodiment of the present invention;

[0014]FIG. 7 is a sectional view of an annular sealing assemblyrepresenting an embodiment of the present invention and having fourannular sealing lips, each being provided with an annular soft metalsealing insert;

[0015]FIG. 8 is a partial sectional view of an annular seal body havinga soft metal sealing insert located in an annular groove of an annularsealing lip having a generally circular or curved cross-sectionalgeometry;

[0016]FIG. 9 is a partial sectional view of an annular seal body havinga soft metal sealing insert located in annular sealing lip having anannular sealing face of substantially planar configuration;

[0017]FIG. 10 is a partial sectional view of an annular flexible highstrength metal seal body having a soft metal sealing insert located inan annular insert recess and being secured in assembly with the annularseal body by a retainer ring;

[0018]FIG. 11 is a partial sectional view of an annular flexible highstrength metal seal body of generally cylindrical internal configurationand having a pair of soft metal sealing inserts located in annularinsert grooves within respective extremities of the annular seal body;

[0019]FIG. 12 is a partial sectional view of an annular flexible highstrength metal seal body defining a plurality of internal annularsealing projections, ridges or bumps each defining an annular insertrecess having an annular soft metal sealing insert retained therein forsealing engagement with a respective annular sealing surface; and

[0020]FIG. 13 is a fragmentary sectional view of an annular flexiblehigh strength metal seal body having an annular internal sealingprojection defining an annular seal recess containing an annular softmetal sealing insert and with the sealing insert shown in sealingengagement with an annular external sealing surface of a tubular memberdisposed in telescoping relation with the annular metal seal body.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Referring now to the drawings and first to FIGS. 1 and 2, ametal-to-metal sealing system embodying the principles of the presentinvention is shown to be provided for sealing a number of joints of awellhead or conduit assembly. The metal-to-metal sealing systemcomprises an annular metal seal body element shown generally at 10having an annular base portion 12 which defines at least one annularsealing lip 14 projecting radially toward and establishingmetal-to-metal sealing engagement with an annular surface 18 which maybe a tapered surface as shown in FIG. 1 or a cylindrical surface asshown in FIG. 2.

[0022] As is shown in greater detail in FIG. 2, the annular metal sealbody 10 of the metal-to-metal sealing system has an annular soft metalsealing insert 14 a, being supported within an insert groove of theannular sealing lip 14 and defining an annular sealing surface 14 b. Theannular sealing surface 14 b may be of curved cross-sectionalconfiguration, cylindrical cross-sectional configuration or any othersuitable cross-sectional configuration without departing from the spiritand scope of the present invention. As is also shown in FIG. 2, theannular seal body of the metal-to-metal sealing system also defines oneor more flexible annular intermediate portions 16 being integral withand extending from the annular base portion 12 and having the annularsealing lip 14 with its soft metal insert 14 a projecting therefrom. Theflexible annular intermediate portions 16 provide the annular seat bodywith a spring-like characteristic, so that the flexible annularintermediate portions 16 become flexed and thus preloaded duringassembly and thus continuously urge the annular sealing lip with itssoft metal insert against an annular sealing surface to maintaininterference sealing therewith. The annular seal body 10 is adapted tobe disposed in substantially concentric relation with a member 26, suchas a tubular member of a wellhead assembly, which member defines atleast one annular sealing surface 18 against which the annular sealinginsert 14 a is pressed in an interference fit relationship when theannular seal body is in functional position. A lead-in chamfer 20 on thecylindrical metal surface or wall 18 provides a means to install theannular metal seal body 10 into its illustrated functional position andto accomplish flexing and preloading of the annular seal body 10, andparticularly its flexible annular intermediate portions 16, to ensureits spring-like forcible metal-to-metal sealing engagement with thecylindrical surface 18. The cylindrical surface 18 is designed to havean axial length that is adequate to ensure that the sealing face of thesoft metal insert is always in metal-to-metal sealing contact with theannular surface 18 regardless of relative movement therebetween inresponse to temperature fluctuations or dimensional changes responsiveto pressure. During assembly, the lead-in chamfer reacts with the softmetal seals 14 a and the annular sealing projections to cause preloadingof the intermediate sections 16 so that the intermediate sections becomeflexed for continuous application of spring force to the annular sealinglips 14 to maintain the soft metal sealing inserts of the annularsealing lips in interference sealing with the annular sealing surface 18of the member 26.

[0023] In the embodiment shown in FIG. 2, the annular seal body 10 alsohas a central web portion 22 that extends radially from the base portion12 to fit into relieved areas 24 a and 24 b in the adjacent faces 26 aand 27 a of annular flanges or other such structures defining themembers 26, for properly positioning the annular seal body at the jointbetween the adjacent faces and ensuring its retention in that location.As shown in FIG. 1, the flanges or other structures defining theadjacent faces 26 a and 27 a can be components of a casing head 30, atubing head 32, a block valve 34, an annulus outlets 36 or a widevariety of other structures where metal-to-metal sealing with internalor external annular surfaces is desired.

[0024] As further indicated in FIG. 1, the metal-to-metal sealing systemof the present invention also can be utilized in a wellhead as (1) anannulus seal 40 between a mandrel casing hanger 42 and the tubing head32, (2) a bushing seal 44 between an annular hanger bushing 46 and thetubing head 32, (3) an annulus seal 48 for tubing hanger couplings 50 ina dual tubing string completion system, and (4) an extended neck hangerseal as shown at 52.

[0025] Since the annular sealing face of the soft metal insert of theannular sealing lip is relatively narrow, may be of roundedcross-sectional configuration and is significantly softer than thecylindrical sealing surface, i.e., from about ⅕^(th) to about ⅓^(rd) theyield stress of the elastic component of the seal, it will not causedamage to the cylindrical sealing surface against which it is pressedwhen the annular sealing body is in functional position with respect tothe cylindrical sealing surface. This small dimensioned sealing facealso permits minor axial misalignment between the sealing element andthe cooperative cylindrical surface to be accommodated, such as forexample between a tubing hanger and the adapter element.

[0026] Tests on wellhead equipment utilizing a metal-to-metal sealingsystem having a soft metal sealing insert, according to the teachings ofthe present invention, have shown that the surface finish at the area ofcontact between the seal element and the cylindrical surface can be asrough as 125 microinches RMS, without jeopardizing the fluid tightnessof the seal. This advantage contrasts significantly with the highlypolished surfaces required in some other metal-to-metal sealing systems,and provides cost reduction opportunities in the manufacturing process.A seal that is an example of the described design passed both API PR2and FMC 500 cycle endurance testing. Testing was done at 5000 psibetween −75° F. and 450° F.

[0027] Additional advantages provided by the present invention include(1) the fact that the cylindrical configuration of the surface againstwhich the sealing surface of the soft metal sealing element is pressedis substantially easier to manufacture than surfaces of otherconfigurations, such as conical, heretofore employed in othermetal-to-metal sealing systems, and (2) no special bolting or clampingarrangements are necessary.

[0028]FIG. 3 illustrates a dual metal-to-metal seal system according tothe teachings of the present invention, wherein an annular metal sealingelement, shown generally at 60, is provided with two axially spacedouter circumferential annular sealing lips 60 a and 60 b being integraltherewith and projecting radially outwardly therefrom. The sealing lips60 a and 60 b are provided for metal-to-metal sealing engagement withannular inwardly facing annular sealing surfaces 62 and 64 of pipe ends66 and 68 that are secured in assembly by an internally threaded pipecoupling 70. The internal end surfaces 62 and 64 of the pipe ends are ofcylindrical configuration and are intersected by annular internalchamfered surfaces 72 and 74 which serve as lead-in chamfers duringinstallation of the annular metal sealing element 60. The annularsealing lips 60 a and 60 b each define annular seal insert recessesreceiving annular soft metal sealing inserts 76 and 78 which projectfrom the respective seal insert recesses for sealing contact with therespective annular sealing surfaces 62 and 64. The annular metal sealingbody 60, as shown in cross-section in FIG. 3, tapers from a relativelythick and substantially rigid generally cylindrical center section 80 torespective annular end sections 81 and 82 thereof so as to defineflexible intermediate sections 84 and 86. The flexible intermediatesections are flexed radially inwardly as, during assembly, the annularsealing lips 60 a and 60 b and the soft metal inserts 76 and 78 traversethe chamfered surfaces 72 and 74 in progress to the cylindrical sealingsurfaces 62 and 64. The force of assembly being applied to the flexibleintermediate sections 84 and 86 of the annular seal body 60 causesradial flexing of the intermediate sections and thus causes the flexibleintermediate sections to become spring loaded or preloaded. This featureenables the annular sealing lips and their soft metal inserts 76 and 78to maintain interference sealing with the annular sealing surfaces 62and 64 even though the respective pipe ends may change in dimension dueto temperature changes, pressure changes, etc. Thus, the seal 60 employsa high strength, elastically deformable metal body to provide energizingforce, and soft metal sealing inserts to provide the sealing mechanism.The soft metal of the annular sealing inserts allows for much highersealing interference, and also permits effective sealing on a sealing orseating pocket surface that might have surface defects due to poorquality machining or surface damage.

[0029] Referring now to FIGS. 4 and 5, an annular sealing elementembodying the principles of the present invention and being showngenerally at 90, defines an annular body section 92 of generallycylindrical outer peripheral configuration and having intermediateflexible body sections 94 and 96 integral therewith. The intermediatebody sections have annular sealing lips 98 and 100 projecting radiallyoutwardly therefrom, and each sealing lip defines an annular seal insertgroove. Annular soft metal sealing elements 102 and 104 are locatedwithin the respective annular seal insert grooves and project radiallyoutwardly beyond the respective annular sealing lips 98 and 100 forsealing contact with respective annular sealing surfaces 106 and 108 oftubular elements 110 and 112. The annular seal body 92 is furtherprovided with an annular outer peripheral web 114 which is receivedwithin an annular seal locating recess 116 that is cooperatively definedby the abutting ends of the tubular elements. The intermediate sections94 and 96 are rendered more flexible as compared with the centralsection 92 by virtue of tapered end surfaces 118 and 120, thuspermitting flexing and spring loading of the flexible intermediatesections by reaction with the internal surfaces of the tubular elementsduring assembly.

[0030]FIG. 6 illustrates a smooth bore metal seal shown generally at122, having an annular seal body 124 defining a generally cylindricalcenter section 126 and having an annular seal locating web 128. Theouter periphery of the annular seal body 124 is tapered from the centralbody section to the respective ends thereof as shown at 130 and 132,thus defining flexible intermediate sections 134 and 136. The respectiveaxial ends of the annular seal body 122 each define annular sealing lips138 and 140, each in the form of an annular sealing lip or projectionhaving an annular sealing insert groove therein. Annular soft metalsealing inserts 142 and 144 are located within the respective annularseal insert grooves and project from the grooves, with an annularsealing portion thereof disposed for sealing engagement with an annularsealing surface of a tubular element or an annular sealing surface forwhich sealing is desired. The annular sealing lips 138 and 140 may havea curved or rounded cross-sectional configuration as shown, or in thealternative may define a more flattened annular surface in which theannular sealing insert is received. The annular sealing lips may alsohave any other suitable geometry, such as generally elliptical,triangular or rectangular, as desired, and the annular seal groove mayhave any suitable cross-sectional configuration, including generallyrectangular as shown in FIG. 5, dove tailed or other undercutconfiguration to provide for retention of the annular soft metal sealinginserts.

[0031]FIG. 7 illustrates an annular sealing element shown generally at150, which may be referred to as an “H” seal and which is useful forsealing with an internal cylindrical element 152 which is disposed insubstantially concentric, spaced relation within abutting tubularmembers 154 and 156. Though not necessary, the tubular members are shownto have tapered connection flanges 158 and 160 that are retained inassembly by a clamp ring 162. The annular sealing element 150 defines acentral web 164 to which is integrally connected a pair of annular sealbody members 166 and 168. The annular seal body member 166 is ofgenerally cylindrical configuration and defines annular sealing lips 170and 172 at respective axial ends thereof. The annular sealing lips eachdefine annular seal retention grooves having annular soft metal sealingelements 174 and 176 located therein for interference sealing with theouter cylindrical surface 178 of the internal cylindrical element 152.Likewise, the annular seal body member 168 is also of generallycylindrical configuration and defines annular sealing lips 180 and 182each having annular seal retainer grooves defined therein and havingannular soft metal sealing inserts 184 and 186 located within therespective seal grooves, with annular portions thereof projecting fromthe seal grooves and disposed in interference sealing engagement withthe internal annular surfaces 188 and 190 of the pipe ends 154 and 156.An annular positioning web 192 projects radially from the centralportion of the annular seal body member 168 and, in operative position,is located within an annular seal location recess that is cooperativelydefined by the joint geometry of the abutting pipe ends 154 and 156.

[0032] The annular seal body members 166 and 168 are sufficientlyflexible that they yield or flex typically during assembly of theannular seal 150 with the tubular member 152 and the pipe ends 154 and156. Thus, when in sealing assembly, the annular seal body members applycontinuous spring force to maintain the annular soft metal seal elementsin interference sealing engagement with the respective annular surfaces.This feature enables the seal to maintain its effective sealingcapability even though the annular members change in dimension due totemperature or pressure fluctuations. Also, the soft metal seal memberswill be deformed by the spring force and the force of assembly and willessentially fill surface imperfections of the cylindrical surfaces andachieve effective sealing. The soft metal seal members will alsoaccommodate situations where the annular members are not of perfectlycircular configuration since the soft metal seals will yield toaccommodate such sealing surface irregularities.

[0033] In the partial sectional view of FIG. 8, an annular seal body 193is provided with an annular sealing lip 194 which is of rounded orsemi-circular cross-sectional configuration and projects radially fromthe annular seal body for sealing engagement with a cylindrical sealingsurface, not shown. An annular soft metal seal member 196 is locatedwithin an annular seal retainer groove defined by the annular sealinglip and projects therefrom for interference sealing engagement with thecylindrical sealing surface.

[0034] In the partial sectional view of FIG. 9, an annular seal body 198has a flexible tapered end section 200 defined by a chamfered surface202. At the axial end of the tapered flexible end section is located anannular sealing lip 204 which projects radially from the annular sealbody in a direction toward an annular surface. The annular sealing lip204 is of generally rectangular cross-sectional configuration anddefines a generally cylindrical or slightly curved outer peripheralsurface 206. The annular sealing lip also defines an annular sealretention groove within which is located an annular soft metal sealinsert 208. The annular seal retention groove may be of generallyrectangular cross-sectional configuration as shown or may be of undercutcross-sectional configuration without departing from the spirit andscope of the present invention.

[0035] It should be borne in mind that the cross section of the softmetal insert for each of the embodiments of the invention set forthherein can be circular, elliptical, triangular, rectangular, orpolygonal, and the seal grooves therefor may be of corresponding ordiffering cross-sectional configuration as desired. The soft metalsealing insert can be used, for example, on the sealing radii of RCMSseals, externally energized metal seals, and SBMS seals. Valve seats maybe replaced with soft metal sealing inserts to minimize machining costs.Soft metal sealing inserts may also be used for ball valve seats, withno need to match lap the valve seat and ball to accomplish effectivesealing. The sealing system of the present invention can be used forsealing on internal or external diameters with equal success. Also, sealdesigns can use multiple inserts (to increase contact area), or a singleinsert having a broad sealing surface. Existing seal designs can bemodified efficiently and at low cost to accommodate the soft insert.Radial bumps of conventional metal-to-metal seals can be flattened and agroove added to simply fabrication of sealing components having softmetal sealing inserts.

[0036] The partial sectional view of FIG. 10 illustrates an annular sealbody structure 210 having at least one tapered flexible end section 212which is defined by a chamfered surface 214 such as discussed above. Theaxial end or ends of the annular seal body define an annular seal recess216 within which is located an annular soft metal seal element 218. Aretainer ring 220, such as a snap ring, is received by the axial end ofthe annular seal body and serves to retain the soft metal sealingelement 218 within the seal recess or groove. Thus, the annular softmetal seal is readily replaceable, so that the annular seal body can bereused even under circumstances where the annular soft metal seal mighthave become damaged during assembly, disassembly, or use.

[0037] Referring now to FIG. 11, the partial sectional view illustratesan annular seal body shown generally at 222, having a central bodysection 224 and intermediate body sections 226 and 228. Flexible axialend sections 230 and 232 of the annular seal body 222 are defined byannular chamfered surfaces 234 and 236. These flexible end sections areprovided with annular seal retention grooves having soft metal sealingelements 238 and 240 retained therein. The soft metal sealing elementseach define annular portions thereof which project radially beyond theannular surface 242 and establish interference sealing with an annularmember. The annular surface 242 may be of cylindrical configuration andmay extend completely to the axial ends of the annular seal body 222 asshown. In this case, the only portions of the seal assembly projectingradially beyond the cylindrical surface 242, except for an annularlocator web 244, the purpose of which is explained above, are thesealing lips and portions of the soft metal sealing elements 238 and240. During assembly of the annular seal body with annular surfaces,such as abutting pipe sections, the chamfered flexible axial ends of theannular seal body can be flexed by chamfered lead-in surfaces in themanner discussed above, to provide the annular seal body with preloadedspring-like characteristics upon assembly for continuous application ofradially directed force to the annular soft metal seals to maintain themin interference sealing with the respective annular sealing surfacescontacted by the soft metal seals.

[0038]FIG. 12 indicates that an annular sealing member shown generallyat 250, embodying the principles of the present invention, may beprovided with more than one or two annular soft metal sealing elements.The annular sealing member is defined by an annular seal body member 252having a central body section 254 which defines circular sealingprojections or lips 256 and 258 each defining an annular seal retainergroove having an annular soft metal seal element 260 and 262 locatedtherein. The annular seal body is provided with flexible axial ends 264and 266 which are defined by chamfered surfaces 268 and 270. Theseflexible axial ends also define annular projections or sealing lips 272and 274 which have annular seal retention grooves containing annularsoft metal seal members 276 and 278. Typically, the plurality of metalseal inserts of the annular sealing member 250 have the same internal orexternal dimension, so that multiple seals can be established on acylindrical surface to enhance the sealing capability of the annularsealing unit. If desired, however, the intermediate seals and the axialend seals or each of the seal inserts may be of differing dimensionaccording to the geometry of the surface or surfaces to be sealed. Theannular seal member 250 is especially adaptable for use as a SBMS seal,with the plurality of annular soft metal seal inserts thus enhancing thesurface contact that is ordinarily possible when seals are used havingonly one or two soft metal seal inserts.

[0039] As shown in FIG. 13, sealing according to the teachings of thepresent invention may be accomplished between telescopically arrangedtubular elements. A tubular element 280 having a cylindrical externalsurface 282 is shown to be telescopically received within a tubularmember 284. To accomplish sealing, the outer tubular member defines aninternal annular sealing projection or lip 286 having an annular sealretention groove 288. An annular soft metal seal is retained within theannular seal retention groove, with an annular portion thereofprojecting radially beyond the annular sealing projection 286 and thusdisposed for sealing engagement with the outer cylindrical surface 282of the tubular element 280. It should be borne in mind that the annularsealing lip may, in the alternative, be located at the outer peripheryof the inner tubular element, causing the soft metal seal to bepositioned for sealing engagement with the inner cylindrical surface ofan outer tubular member.

[0040] As will be readily apparent to those skilled in the art, thepresent invention may easily be produced in other specific forms withoutdeparting from its spirit or essential characteristics. The presentembodiment is, therefore, to be considered as merely illustrative andnot restrictive, the scope of the invention being indicated by theclaims rather than the foregoing description, and all changes which comewithin the meaning and range of equivalence of the claims are thereforeintended to be embraced therein.

What is claimed is:
 1. In combination with a wellhead assembly whichincludes at least first and second adjacent components and first andsecond generally annular sealing surfaces that are each formed on acorresponding one of the components, a metal-to-metal sealing elementcomprising: an annular base; an annular sealing lip which projectsradially toward at least one of the first and second sealing surfacesand which comprises a seal retaining groove; a soft metal sealing insertwhich is disposed within the seal retaining groove and which in useengages the at least one sealing surface; and an annular intermediateportion which extends between the base and the sealing lip; wherein theintermediate portion presses the sealing insert against the at least onesealing surface in an interference fit relationship.
 2. A wellheadassembly according to claim 1, wherein at least one of the first andsecond components includes a frusto-conical surface intersecting thesealing surface, and wherein the frusto-conical surface functions as alead-in chamfer for installation of the sealing element.
 3. A wellheadassembly according to claim 1, wherein the sealing element comprises aplurality of sealing lips, each of which is connected to the base by acorresponding intermediate portion and each of which includes a sealretaining groove within which a soft metal sealing insert is disposedfor metal-to-metal sealing engagement with at least one of the first andsecond sealing surfaces.
 4. A wellhead assembly according to claim 3,wherein the sealing element comprises two sealing lips, each of which ispositioned opposite a corresponding one of the first and second sealingsurfaces.
 5. A wellhead assembly according to claim 4, wherein thesealing element further comprises a web portion intermediate the sealinglips to locate and retain said sealing element in functional positionwith respect to the first and second sealing surfaces.
 6. A wellheadassembly according to claim 3, wherein the first and second componentsare arranged concentrically relative to each other and wherein thesealing element comprises a generally U-shaped cross-sectionalconfiguration and inner and outer sealing lips, each of which includes aseal retaining groove within which a soft metal sealing insert isdisposed for metal-to-metal sealing engagement with the first and secondsealing surfaces.
 7. A wellhead assembly according to claim 3, whereinthe first and second components are arranged coaxially relative to eachother and wherein the sealing element comprises a generally step-shapedcross-sectional configuration and inner and outer sealing lips, each ofwhich includes a seal retaining groove within which a soft metal sealinginsert is disposed for metal-to-metal sealing engagement with the firstand second sealing surfaces.
 8. A wellhead assembly according to claim3, further comprising a third component which includes a correspondingthird sealing surface, and wherein the sealing element comprises agenerally H-shaped cross-sectional configuration and at least threesealing lips, each of which includes a seal retaining groove withinwhich a soft metal sealing insert is disposed for metal-to-metal sealingengagement with the first, second and third sealing surfaces.
 9. Awellhead assembly according to claim 8, further comprising a fourthcomponent which includes a corresponding fourth sealing surface, andwherein the sealing element comprises four sealing lips, each of whichincludes a seal retaining groove within which a soft metal sealinginsert is disposed for metal-to-metal sealing engagement with the firstand second sealing surfaces.